The present invention relates generally to medical devices, and more particularly to an improved tip design for a multi-lumen catheter.
Multi-lumen catheters are used for a variety of applications when it is necessary to have two separate fluid pathways. One such application for a multi-lumen catheter is for use in a hemodialysis process. During hemodialysis, a dual-lumen catheter can be employed to simultaneously accommodate opposing blood flow. More specifically, one lumen carries blood from a patient to a dialysis machine where it is processed for the removal of toxins, while the opposing lumen returns the purified blood to the patient.
Multi-lumen catheters are well known in the art. An example of such a catheter used for hemodialysis is shown in U.S. Pat. No. 4,808,155 to Mahurkar, which discloses a double lumen catheter including a return lumen and an inlet lumen. The return lumen extends along the entire length of the catheter to an opening at the distal end of the catheter. The inlet lumen is shorter than the return lumen and terminates at an opening substantially displaced from the return opening. The separation of the two openings is designed to prevent the mixing of treated blood with non-treated blood. Problems may result from this design, however. First, the openings may become partially or totally occluded by the vessel wall or by a build up of blood components. Second, due to the pressure of fluid exiting the return lumen, a whipping action can occur, wherein the sharp edges of the tip of the catheter lashes back and forth within the vein of a patient, causing trauma to the inside wall of the vein. This whipping action can also cause clots to form around the outside surface of the catheter, obstructing blood flow to and from the openings.
To overcome the problems of the Mahurkar device, Cruz et al. (U.S. Pat. No. 5,571,093) proposed a multi-lumen catheter with a bolus tip, containing a radial passage that forms a port through the side of the bolus. In one embodiment, a first and second lumen are in fluid communication with the port. In another embodiment, the bolus tip contains two ports in the same side, one port providing an opening for the first lumen while the other port provides an opening for the second lumen. In both embodiments, the port nearest to the distal end of the bolus tip is created by removing a piece of the body around greater than 180° of the circumference of the body. According to Cruz et al., this configuration causes the velocity of the fluid passing over the bolus to decrease, thereby limiting the whipping action. However, because the outlets of the first and second lumen are located on the same side of the bolus, the problem of mixing treated and non-treated blood exists. Accordingly, there is a need for a catheter tip configuration that maintains adequate separation of treated and non-treated blood and that reduces the traumatic effects associated with whipping. In addition, there is a need for a catheter tip that will not easily become occluded.
It is therefore an object of this invention to provide an improved bolus tip design for a multi-lumen catheter that provides an optimum separation of fluids to be simultaneously injected into and aspirated from a patient's body.
It is a further object of this invention to provide an improved bolus tip design for a multi-lumen catheter that reduces the trauma to the vein of a patient associated with insertion of the catheter and whipping.
It is still a further object of this invention to provide an improved bolus tip design for a multi-lumen catheter that will allow the continuous transfer of fluid to a patient despite the presence of obstructions.